Respiratory and hematological adaptations of young and older Aymara men native to 3600M

This paper reports the results of a study designed to test the hypothesis that an inevitable concomitant of aging at high altitudes is chronic mountain sickness resulting from excess erythrocytosis secondary to exaggerated hypoxemia caused by aging processes in the respiratory system. It compares age differences in respiratory system function in oxygenating the blood measured as percent O₂ saturation of arterial hemoglobin during wakefulness and sleep and in erythrocytosis measured as hemoglobin concentration in 17 young (22-35 years) and 16 older (47-68 years) rural and urban resident Bolivian Aymara men, healthy lifelong residents of 3,500-4,000 m who were tested at 3,600 m. The results do not support the hypothesis. Older urban men are significantly more hypoxemic during wakefulness and sleep than young urban men, while there are no age differences in the degree of hypoxemia among the rural residents. However, older urban men do not have the higher hemoglobin concentration predicted by the hypothesis. Both urban and rural older men have lower hemoglobin concentration than their young counterparts, a finding not attributable to age differences in nutritional status or testosterone concentration. Despite their relatively low hemoglobin concentration, older men have estimated arterial O₂ content in the normal sea level range for young men and in this sense retain the capacity to adapt to high altitude at least through the seventh decade of life.